California is one of only three states that has any guaranteed parental leave for employees and none of them offer full pay. California workers currently receive 55% of their pay when they go on paternity or maternity leave. This San Francisco measure will require employers to pay the remaining 45%.

The U.S. and Papua New Guinea are the only countries that do not have paid paternity leave protected by law, according to the International Labor Organization.

Data from the ILO shows that the current U.S. policy is much smaller compared with other countries, particularly in Europe. Finland, for instance, offers new parents 54 fully paid days off, plus an additional 158 days for either parent.

Whether or not other U.S. cities will follow suit, paid parental leave has become a major issue in this year's presidential election for Democratic candidates. Both Bernie Sanders and Hillary Clinton are advocating for 12 weeks of paid leave.